Telescopic rotor blades and brakes therefor



May 5, 1953 v. lsAcco 2,637,406

TELESCOPIC ROTOR BLADES AND BRAKES THEREFOR Filed Jan. 9, 1948 Fig .Z

, Aller/ley Patented May 5, 1953 TELESCOPIC ROTOR BLADES AND BRAKES THEREFOR Vittorio Isacco, London, England Application January 9, 1948, Serial No. 1,458 In Great Britain October 7, 1947 parachutes and helicopters as has been described in the specification of my Patent No. 2,523,216. l

According to the invention, there is provided a brakefforthe purpose of delaying the opening oi` the elements constituting ea ch blade of the sustaining propeller or propellers. On account of practical necessities. a small play must be provided for the easy sliding movement of the elements when they extend outwards under the action of the centrifugal force, this giving way in practice to a rather fast opening of the blades, which fast opening has proved to be undesirable.

The present brake is unique for the blades of a rotor, and its pressure 'can be regulated before flight according to flight requirements.

The brake may be common to the blades or individual brakes may be provided for the blades.

UThe. common brake does not compensate for the .differences in the sliding of the elements of one blade withrespect to those of other blades and therefore it is desirable to provide'the blades with 4individual brake devices in order to compensate for the differences of friction due to manufacturing inequalities; and if desired the individual brakes may be the sole braking means employed.

.Another feature of the invention is that the same collective brake system can be utilized to retract all the blades at the same time when the speed of rotation is sufciently low. This is effected by operating on a lever which acts as a brake between any part of the common brake and any part of the case or hub, or on any non-rotati `ing part of the rotor.

In the accompanying drawings:

Fig. l is a top plan view of a propeller fitted with the general and individual brak-e devices in accordance with the present invention.

Fig. 2 is a cross-sectional View corresponding to line 2-2 of Figure l.

Fig. 3 is an enlarged detail view of an individual brake device given as an example.

In Figs. l and 2, the central shaft I shown as tubular is stationary, being rigid with the nonrotating case or body 2. The rotor hub, composed o portions 3a, 3b and 3e, rotates freely around 'the .shaft I by means of two ball-bearings 4 and 5.

Nuts 6 and l and the spacer 8 hold the hub in position on the shaft I. The main hub portion 3ais journalled on said bearings 4 and 5 and nulo portion 3b comprises an upper extension rigidly secured to the upper end of the portion 3a by screws 8. The portion 3c comprises an annular i til 3 claims. (c1. 17o-160.11)

ilange extending radially from the portion 3a, as will be described hereinafter.

The rotor blades Il) are mounted on the upper hub portion 3b, two blades being shown as an example. These blades are of the telescopic type and are diafrramrnatically shown as including root elements 45, intermediate elements 4d and tip elements 56 which may be closed at their outer ends by flanged plugs 5I. The root elements It are closed at their inner ends by bottom plates 53 against which the intermediate and tip elements abut when the blades are collapsed or retracted, as shown. These blades may be of the type shown in any aforementioned patents, particularly No. 2,523,216.

The root elements l5 are mounted on the hub portion 3b by means of bushings I4 carried by brackets I I that are secured to the root elements by bolts i2 and spacers I3. Each bushing I4 is iournalled on a hollow shaft I5 that is supported vertically on an axis I-I by a hollow fork I6, these axes'I-I forming the hinging axis of the blades. The locking device which maintains the blades in this position, has already been described in the specification of my Patents Nos. 2,457,376, 2,458,855 and 2,523,216.

In the drawings, forks I6 are shown for simplicity, attached to the horizontal forks I8 by means of rivets Il. rIhe horizontal forks I8 are inclined or extended angularly towards the leading edges of the blades as has been described in the aforementionedv Patents 2,458,855 and 2,523,216. The horizontal forks i8 are hinged around a shaft 56 having a substantially horizontal axis III--III passing through the upper hub 3b. A nut 26 maintains the shaft I9 in position, antifriction rings 2i being provided between the ends of the forks` I8.

The upper elastic stops 22 and the lower ones 23 are fitted 0n or around the upper hub part 3b, thesev stops limiting the yupward and downward flapping movements of the blades as described in the aforementioned Patent No. 2,457 ,376.

The common brake which will delay the openingV of the blades when subject to rotation by any means will now be described.

In the example shown, this brake is constituted by a pulley 25 capable of rotating around the lower hub 3c while bearing on the flange 3c of the said hub. A nut 26 is screwed onto the hub 3a I8, the hub 3a, 3b, 3c, the pulley 25. andthe nut.

2B, the pulleys 28, supports 29 and'cables 21, constitute normally a single unit that rotates freely around the central shaft I. movement of the pulley 25 and the cables or` wires 21 to the hub 3b, 3c, takes place' when. theblades are extended under the centrifugal force generated during rotation. rlhat is tov say, the outward movement of the elements acts on the wires 21 which in turn give the pulley 25 a relative movement of rotationin regard to the hub 3a. Pulley 25 must rotate in order for the blades to extend, and the speed of openingor extension of the blades will depend on the friction existing between the pulley 25 and the hub iiange 3c.

The wires 2l are wound around pulley 25 in same directions, thus rotating the pulley 25- in the same direction as indicated by arrows b when the blades extend centrifugally.

Individual adjustable brakes 3! may be employed to cooperate with the wiresl 2l' to equalize any difference in the sliding movements of two opposite blades and these brakes may either supplement or substitute for the commen brake, if desired. They are, in the. examplel indicated in the drawings, fitted inside the end bracket Il' of the blades. The wires 21 pass through these brakes 3i] before passing inside the blade elements, to be finally attached to any partof the'tips elements 5t]v of the blades.

The individualbrake 311,y given. as' an example, is shown on a largerscale in. Fig. 3.` The. wire 21 passes between two appropriately bent plates orjaws 3| and 3.2, these plates being articulated at 33 to a support 35 i'lxed on both sides to the bracket Il. A screw 34 acts on the plates so as to exert the desired pressure on the Wire 21, and thusv brake its sliding movement when the blades are extended or retracted.

Thus by a' convenient regulation of the-individual brakes 30 the'rate of simultaneous slidingmovement of the elements of each blade can be made almost equal, and by regulating the common brake by pressure of the nut- 2S and flangef 3c against pulley 25v the speed of opening' of all the blades can be achieved as desired. The individual brakes may be dispensed with if desired.

Figs. l and 2 show clearly how the blades can be made to retract when the speed of rotation of the rotor has sufficiently decreased after landing, and eventually how the body of the apparatus and the machine or man carried by the` propeller can be made to rotate in the same direction as the propeller.

In the example, the pulley 25 is extended and cndsin a conical surface 25a. A rod 36 36a, can be pushed upwards accordingto the arrow c in the example, so as to come into contact with the conical surface 25a of the pulley 25. The part 36a of the rod is fitted at its end with a friction segment 31. The rod 36 36a is guided by means of a bracket 38 fixed to the case `2. A spring gpushesthelever 35 downwardsl so as However, a` relativel normally to hold the segment 31 away from the surface 25a.

Upward pressure on the rod 36 36a, will have the effect of retarding the speed of rotation of the pulley 25 with regard to that of the hub 3a and the blades giving Way to a relative movement of rotation of the pulley 25 according to arrow d which is opposite to the.y relative: movement during the opening of the blades. The result will be, that wires 21 will be pulled back in opposite direction to arrows a, and will be wound around the. pulley 25 until. the retraction of the blades is complete'. If thev braking effect between 25a and 31 persists after the retraction of the blades (rod 36' not. released in time), the result will be a braking effect on the remaining speed of rotation of thel rotor as a whole, and its stoppage earlier than without this braking effect.

It' will also be evident that if the man descending with the machine or parachute momentarily depresses the rodV 35 the4 body of` the; machine or parachute and. therefore the man, will bepartially turned` It is also clear that the main. condition.4 for the retractionof the blades, is; thatV the braking effect on 31 must be superior to the braking effect` of the pulley 25 on 3c. Friction rings 25o may be provided on. the pulley 25 for, cooperation with the elements 26 and 3c.

It is evident that the invention isv not limited by the devices described, and that other modifications can be utilised as long, as the principles are not altered.

For example, the collective and separate brakes for the regulation of the opening of the elements can altogether be different.

The brake system for the retraction of. the blades can be different,v and can be effected between any part of the rotating hub or of the brake-pulley and any part of. the case' or body of the propeller; Other flexible connecting elements, such as metal or canvas tapes' can be used, instead of the cables 21.

Also, conical surface 25a or friction' segment 31 can be constituted by several strips, or a. complete ring.

I claim:

l. A rotor for a rotatable wing aerial apparatus, comprising a rotatable shaft', a plurality of telescopic propeller blades mounted on said shaft to rotate therewith, a cable reel on said shaft, retractive cables connected between said reel and the tip elements of said blades, said reelV being rotatable on said shaft to wind said cables thereon to retract said telescopic blades and to pay out said cables upon extension of said blades by centrifugal action when said shaft is rotated, means for holding said reel against rotation with said shaft to wind said cables thereon, manually adjustable brake means between .said reel and said shaft for exerting a selected constant resistance to relative rotation between said shaft and reel, and manually adjustable brake means on the base end of each of said blades and engaging the respective cable to selectively retard the paying out of the individual cables to ensure uniform extension of said blades.

2. A rotor for a rotatable wing aerial apparatus, comprising a rotatable shaft, a plurality of telescopic propeller blades mounted on said shaft to rotate therewith, a cable reel on said shaft,

' retractive cables connected between said reel and the tip elements of said blades, said reel being rotatable on said shaft to wind said cables thereonto retract said telescopic blades and to pay out said cables upon extension of said blades by centrifugal action when said shaft is rotated, means for holding said reel against rotation with said shaft to wind said cables thereon, anal manually adjustable brake means between said reel and said shaft for exerting a selected constant resistance to relative rotation between said shaft and reel.

3. A rotor for a rotatable Wing serial apparatus, comprising a rotatable shaft, a plurality of telescopic propeller blades mounted on said shaft to rotate therewith, a cable reel on said shaft, retractive sables connected between said reel and the tip elements of said blades, said reel being rotatable on said shaft to Wind said cables thereon to retract said telescopic blades and to pay out said cables upon extension or said blades by centrifugal action when said shaft is rotated., means for holding said reel against rotation with said shaft to Wind said cables thereon, and manually adjustable brake means on the base References Cited in the le of this patent UNITED STATES PATENTS lo Number Name Date 266,165 Lawhead Oct. 17, 1382 1,344,640 Leinweber June 29, 1920 1,478,063 Schiesari Dec. 18, 1923 1,969,077 Howe Aug. 7, 193e 15 2,052,781 Lindsay Sept. 1, 1936 2,108,245 Ash Feb. 15, 1933 2,163,482 Cameron June 20, 1939 2,364,496 Vogel Deo. 5, 12%

FOREIGN PATENTS 20 Number Country Date 531,241 Great Britain Jan. 1, 1Sl1 

